Former President Jimmy Carter condemned possible chemical weapons attacks in Syria, but called for a “peace conference” and working with the United Nations, rather than using a military solution.

In a statement Friday from the Carter Center, the former president said that the U.N. investigation into possible chemical weapons attacks in Syria is under way and urged against action in the country without U.N. support.

“It is imperative to determine the facts of the attack and present them to the public. Those responsible for the use of chemical weapons must bear personal responsibility,” Carter said in the statement. “The chemical attack should be a catalyst for redoubling efforts to convene a peace conference, to end hostilities, and urgently to find a political solution.”

The Carter Center urged against a military response to possible chemical weapons use without a U.N. mandate, saying the action would be “illegal under international law and unlikely to alter the course of the war.”